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Re: Heating and cooling tanks
Bob Olesen wrote, in part:
> All this talk about heating and cooling, especially the economic
> considerations with larger tanks, got me to thinking (ouch). At first
> I was
> going to suggest a spa heater but that image triggered a memory of
> an A.C. tech told me once while servicing my A.C. and watching the
> pool guys
> install (yet) another spa heater out back.
> I should point out that I'm not a technical or mechanical type person
> so I
> may be way, way off base here. Feel free to correct me.
> As I understand it, a condenser produces heat while laboring under
> and doing it's compressing thing, as well as cold when the freon or
> other gas
> is allowed to expand once again. Everybody has a refrigerator, right?
> there was someway to tap into a nearby existing refrigerator, one
> theoretically obtain heat from the condenser and cooling from the
> compartment for little more cost than the effort to do so.
> I think...
> Even if there was no refrigerator right nearby the tank, I've seen
> little box 'fridges sold new for less than $100.00 on sale and even
> units for less than $200.00 any day of the week. That's a lot less
> than the
> cost of a chiller, right? Used, they're practically given away. One
> probably fit under the cabinet of a big 1000 gal tank and keep frozen
> food and chemicals inside as well as cooling and/or heating the
> If one could figure a way to turn the inside into a reservoir to run
> through, you could probably do multiple tanks, a fish room even with
> dedicated unit. The heat, of course, would come from rigging up a
> type system for the compressor itself to absorb and carry away the
> heat it
> produces. This would be the hard part.
> The A.C. tech told me a normal compressor could easily heat my 800(?)
> gal spa
> to over 100 degrees. I don't know if this guy was totally whack case
> or what
> but he did install and service a 3.5 ton A.C. unit on that side
> I though this concept might be worth mentioning anyway.
> For instance, why hasn't this been done? It seems like there must be
> something wrong here or this would have been implemented more by now
> or at
> least appear in aquarium discussions somewhere. There's no way I'm
> the first
> to have thought of it.
> Planted tanks, with the lighting levels most successful ones employ,
> sure use an economical means of cooling things down.
Excellent thoughts about DIY heat pumps, which is what the heating and
cooling industry calls ACs when you use them for heat rather than
cooling. Heat pumps have some advantages and disadvantages vis-a-vis
furnaces, burners, and electric coils. I would like to add a few
All ACs & chillers are basically heat movers -- they absorb heat energy
from one location (evaporator coils) and dump it in another (condenser
coils). Home brewers have been chilling their draft beer by running it
through coils placed in small (dorm size) refrigerators for years.
This is also a way to chill an aquarium, although it costs a lot of
energy gathering the heat, pumping the water (on draft beer setups, the
CO2 does the pumping).
Tapping (sorry for the pun) into a small fridge (or your home fridge)
for the collected heat rather than the "colelcted cold" seems just a
Potential problems using a refridgerator as a heat pump (or chiller):
If you make a heat exchanger and have the condenser (or evaportor)
coils submerged (they weren't designed for submersion), could corrosion
be a problem?
Will the energy to pump the water, seriously detract from the
efficiency -- won't it add a lot of heat since effective cooling
requires a high flow. I tried chilling water this way and found the
efficiency problems challenging to say the least (what? me say the
least?). For example, a cooling (or heating coil) presents substantial
static pressure -- maintaining water flow requires subtantial output to
overcome this and that costs energy.
I spoke to my father-in-law about the situation (he's a heating-cooling
contractor) -- he started to explain the practical difficulties to me
regarding changing the temperature of fluids and I soon gave up on the
project. It seemed to me that workable systems would be too
complicated, too expensive operate, to unreliable --- or all three.
But I'm no inventor. Someone ought to be able to come up with a DIY
design. The savings could come from the fact that you are paying to
collect the heat anyhow with your home fridge -- the challenge is to
not use up all that savings and more moving that heat into you tank.
If you drink a lot of beer -- I don't -- you might realize an economoy
of scale here somehow -- or at least you might convince the spouse of
that when the bill for the stainless steel tubing, pumps, thermostatic
relays, refrigerator, etc. comes in. :-)
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